For centuries, efforts have been expended to create illusions of motion, disappearances and appearances without apparent explanation. Optics did a great deal to enhance this slight of hand phenomenon by being light to mask, or channel angles of vision at the will of a practitioner.
Technological advances in plastics, lithorgraphy and mass production finally brought this art form beyond individual stage performances to the hands of every individual. The mass circulation of lenticular novelty devices transformed the passive audience into active participants. From that time on, imaginations have been sparked to convert these hand held novelty devices to practical use.
Attempts have been made to animate portions of billboards, general advertising signs, traffic control signs, and reflectors by the same optical means. However, the angle of change required to activate motion or change was too great to be practical for attracting attention at substantial distances from the lenticular surface. U.S. Pat. No. 2,951,419 was issued for the animation of reflectors and reflective signs for roadside use. The message change rate proved too slow to correspond with small angular changes related to an impending warning sign some 300 or more feet relative to a viewer's subtending motion. The relationship between aperture and focal length produced light rays with included, or divergent angles must too large to affect message changes or motion at the sign face with it subtended an angle of less than twenty degrees. Also, the structural juxtaposition of the lenticular lens and the reflective carrier sheet reduced the reflected light below acceptable standards for highway or roadside use because of spherical aberrations caused by the individual lens ridges and the diffusing nature of the short focal length directly on the back side of the lens sheet. U.S. Pat. No. 3,590,509 applied the multiple message characteristics of lenticular optics to large, single message lens relief letters with varying focal lengths, backed by reflective patterns spaced from the back of the lens. This attempt was to give a sign facing an appearance of sparkling or random background motion. However, there was no regard for uniform or controlled focal lengths because the message was stamped into the sign face. Therefore the passive motion was happenstance at best and, at distances of fifty feet or more, only isolated and imperceptible movement prevailed.
U.S. Pat. No. 3,314,179 attempts to resolve the minimum angle changes which occur at great distances by motorizing the lenticular device for continuous motion. The specific linguistic description used in this patent describes the separation of the lenticular screen from the graphic display as a friction reducing function and a means to minimize physical damage to the lenticular ridges. This electrical approach has its greatest benefits when the observer is standing still. But when an observer is in motion, the effects can vary widely according to the speed of the device in relation to the observers motion. In areas where ordinances prohibit the use of outdoor signs with moving parts; flashing lights, or physical movement in general; or where electrical facilities are not available, this approach is not practical. Further, there is no reference, acknowledgement, or solution offered for surface light reflections and light interferences caused by the "friction reducing" space separating the lens sheets and message carrier when not backlighted. It is apparent from the preceding brief that prior art has not addressed the problem of supplying a lenticular sign or lenticular signaling device with predictable motion prescribed for specific viewing situations without an applied energy source. Further, the prior art does not provide for a lenticular device which does not substantially deminish the lighting characteristics of the source used to illuminate the lenticular screen.